This invention relates to compositions for extending seal life. These compositions contain a hydrocarbyl mercaptan and a sulfur containing antiwear or extreme pressure agent, a basic nitrogen compound, or mixture thereof. The invention also relates to lubricants, greases and functional fluids containing the same.
Seals are used in design and manufacture of engines, gear assemblies and transmissions to maintain the fluid or lubricant within the apparatus. The seals come in contact with the lubricant and may, under operating conditions, lose their elasticity and become brittle. Often the deterioration of seals is affected by the additives present in the lubricant. To solve problems associated with seal deterioration, formulators of lubricants have used additives to protect seal or cause swelling of the seals. Sulfolenes are an example of such seal swell agents.
Seals are typically made of nitrile rubber, fluoroelastomers and polyacrylates. It is desirable to use low cost seals in designing equipment. Accordingly, a need exists for improving the operating life of seals, especially nitrile and polyacrylate seals.
This invention relates to compositions containing a sulfur containing antiwear/extreme pressure agent, basic nitrogen compound or a mixture thereof together with a hydrocarbyl mercaptan. The compositions may additionally contain a phosphorus or boron antiwear or extreme pressure agent, a dispersant or an overbased metal salt. The invention also relates to lubricants, functional fluids, and concentrates containing the same. Seals, e.g. nitrile, polyacrylate, and fluoroelastomer, in contact with these composition have reduced deterioration. With the use of these compositions, lubricants, and functional fluids, the useful life of seals is extended.
The term xe2x80x9chydrocarbylxe2x80x9d includes hydrocarbon as well as substantially hydrocarbon groups. Substantially hydrocarbon describes groups which contain heteroatom substituents that do not alter the predominantly hydrocarbon nature of the substituent. Examples of hydrocarbyl groups include the following:
(1) hydrocarbon substituents, i.e., aliphatic (e.g., alkyl or alkenyl) and alicyclic (e.g., cycloalkyl, cycloakenyl) substituents, aromatic-, aliphatic- and alicyclic-substituted aromatic substituents and the like as well as cyclic substituents wherein the ring is completed through another portion of the molecule (that is, for example, any two indicated substituents may together form an alicyclic radical);
(2) substituted hydrocarbon substituents, i.e., those substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; those skilled in the art will be aware of such groups (e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro, nitroso, sulfoxy, etc.);
(3) heteroatom substituents, i.e., substituents which will, while having a predominantly hydrocarbon character within the context of this invention, contain an atom other than carbon present in a ring or chain otherwise composed of carbon atoms (e.g., alkoxy or alkylthio). Suitable heteroatoms will be apparent to those of ordinary skill in the art and include, for example, sulfur, oxygen, nitrogen and such substituents as, e.g. pyridyl, furyl, thienyl, imidazolyl, etc.
In general, no more than about 2, preferably no more than one heteroatom substituent will be present for every ten carbon atoms in the hydrocarbyl group. Typically, there will be no such heteroatom substituents in the hydrocarbyl group. Therefore, the hydrocarbyl group is purely hydrocarbon.
As described above, the lubricants and functional fluids contain (A) a sulfur containing antiwear or extreme pressure agent and/or a basic nitrogen compound in combination with (B) a hydrocarbyl mercaptan. In one embodiment, (A) is present at concentrations in the range of about 0.05% to about 10% by weight, or preferably, from about 0.1% up to about 8%, or more preferably from about 0.3% up to about 7%, more preferably from about 0.5% to about 5% by weight. Here, as well as elsewhere in the specification and claims, the range and ratio limits may be combined. In one embodiment, (A) is used in crankcase lubricants in an amount from about 0.01% up to about 6%, or preferably from about 0.05% up to about 5%, or more preferably from about 0.1% up to about 3% by weight. In another embodiment, (A) is used in a driveline or transmission fluid, in an amount from about 0.5% up to about 10%, preferably from about 1% up to about 7%, or from about 2% up to about 6% by weight. When a mixture of sulfur containing compounds and basic nitrogen compounds is used, then each component may be independently present in the amounts given above.
Sulfur Containing Antiwear/Extreme Pressure Agent
The sulfur containing antiwear and/or extreme pressure agent (A) includes sulfur compounds, such as sulfurized olefins, metal thiophosphates, organic ammonium thiosulfates, or mixtures thereof. The sulfur compounds include mono- or polysulfide compositions, or mixtures thereof. The sulfur compounds are generally characterized as having sulfide linkages containing an average from 1 up to about 10, or from about 2 up to about 8, or from about 3 up to about 4 sulfur atoms. In one embodiment, the organic polysulfides may be a mixture of di-, tri- or tetrasulfide materials, preferably having a majority of trisulfide. Materials having at least 70% trisulfide are preferred, with materials containing greater than 80% trisulfide more preferred.
In one embodiment, the sulfur containing antiwear or extreme pressure agent is a sulfurized compound. Materials which may be sulfurized include oils, unsaturated fatty acids, unsaturated fatty esters, olefins, terpenes, or Diels-Alder adducts. Oils which may be sulfurized are natural or synthetic oils, including mineral oils, lard oil, carboxylic acid esters derived from aliphatic alcohols and fatty acids or aliphatic carboxylic acids (e.g., myristyl oleate and oleyl oleate), and synthetic sperm whale oil substitutes and synthetic unsaturated esters or glycerides.
The unsaturated fatty acids generally contain from about 8 to about 30, or from about 12 to about 24 carbon atoms. Examples of unsaturated fatty acids include palmitoleic acid, oleic, linoleic, linolenic, erucic acid, lard oil acid, soybean oil acid, tall oil and rosin acid.
The unsaturated fatty esters include fatty oils, that is, naturally occurring or synthetic esters of glycerol and one or more of the above fatty acids. Examples of fatty esters include animal fats, such as Neat""s-foot oil, lard oil, depot fat, beef tallow, vegetable oils including cottonseed oil, corn oil, safflower oil, sesame oil, soybean oil, and sunflower seed oil. The unsaturated fatty esters also may be prepared by esterifying alcohols and polyols with a fatty acid. The alcohols include the above described mono- and polyhydric alcohols, such as methanol, ethanol, propanol, butanol, ethylene glycol, neopentyl glycol, and glycerol.
The olefins, which may be sulfurized, contain at least one olefinic double bond, which is defined as a non-aromatic double bond. The olefins include the dienes described below. In its broadest sense, the olefin may be defined by the formula R*1R*2Cxe2x95x90CR*3R*4, wherein each of R*1, R*2, R*3, and R*4 is hydrogen, or an organic group. In general, the R* groups in the above formula which are not hydrogen may be represented by xe2x80x94(CH2)nxe2x80x94A, wherein n is a number from 0 to about 10 and A is represented by xe2x80x94C(R*5)3, xe2x80x94COOR*5, xe2x80x94CON(R*5)2, xe2x80x94COON(R*5)4, xe2x80x94COOM, xe2x80x94CN, xe2x80x94X, xe2x80x94YR*5 or xe2x80x94Ar, wherein: each R*5 is independently hydrogen, or a hydrocarbyl group, with the proviso that any two R*5 groups may be connected to form a ring of up to about 12 carbon atoms; M is one equivalent of a metal cation (preferably Group I or II, e.g., sodium, potassium, barium, or calcium); X is halogen (e.g., chloro, bromo, or iodo); Y is oxygen or divalent sulfur: Ar is an aromatic group of up to about 12 carbon atoms.
The olefinic compound is usually one in which each R group which is not hydrogen is independently alkyl, alkenyl or aryl group. In one embodiment, R*3 and R*4 are hydrogen and R*1 and R*2 are alkyl or aryl, especially alkyl having from 1 up to about 30, or up to about 16, or up to about 8, or even up to about 4 carbon atoms. Olefins having from 2 up to about 30, or from about 3 up to about 16 (most often less than about 9) carbon atoms are particularly useful. Olefins having from 2 up to about 5, or from 2 up to about 4 carbon atoms are particularly useful. Isobutene, propylene and their dimers, trimers and tetramers, and mixtures thereof are especially preferred olefins. Of these compounds, isobutylene and diisobutylene are particularly desirable. In one embodiment, the organic polysulfides may be a mixture of di-, tri- or tetrasulfide materials, preferably having a majority of trisulfide. Materials having at least 70% trisulfide are preferred, with materials containing greater than 80% trisulfide more preferred.
In another embodiment, the organic polysulfide comprise sulfurized olefins prepared by the sulfochlorination of olefins containing four or more carbon atoms and further treatment with inorganic higher polysulfides according to U.S. Pat. No. 2,708,199.
In one embodiment, the sulfurized olefins may be produced by (1) reacting sulfur monochloride with a stoichiometric excess of a lower olefin, e.g. containing two to about seven carbon atoms, (2) treating the resulting product with an alkali metal sulfide in the presence of free sulfur in a mole ratio of no less than 2:1 in an alcohol-water solvent, and (3) reacting that product with an inorganic base. This procedure is described in U.S. Pat. No. 3,471,404, and the disclosure of U.S. Pat. No. 3,471,404 is hereby incorporated by reference for its discussion of this procedure for preparing sulfurized olefins and the sulfurized olefins thus produced. Generally, the olefin reactant contains from about 2 to about 5 carbon atoms and examples include ethylene, propylene, butylene, isobutylene, amylene, etc.
The sulfurized olefin may also be prepared by reacting, under superatmospheric pressure, the olefin with a mixture of sulfur and hydrogen sulfide in the presence, or absence, of a catalyst, followed by removal of low boiling materials. The olefins which may be sulfurized, the sulfurized olefin, and methods of preparing the same are described in U.S. Pat. Nos. 4,119,549, 4,199,550, 4,191,659, and 4,344,854. The disclosure of these patents is hereby incorporated by reference for its description of the sulfurized olefins and preparation of the same.